1use crate::{PlatformDispatcher, Priority, RunnableVariant};
  2use scheduler::Instant;
  3use scheduler::{Clock, Scheduler, SessionId, TestScheduler, TestSchedulerConfig, Yield};
  4use std::{
  5    sync::{
  6        Arc,
  7        atomic::{AtomicUsize, Ordering},
  8    },
  9    time::Duration,
 10};
 11
 12/// TestDispatcher provides deterministic async execution for tests.
 13///
 14/// This implementation delegates task scheduling to the scheduler crate's `TestScheduler`.
 15/// Access the scheduler directly via `scheduler()` for clock, rng, and parking control.
 16#[doc(hidden)]
 17pub struct TestDispatcher {
 18    session_id: SessionId,
 19    scheduler: Arc<TestScheduler>,
 20    num_cpus_override: Arc<AtomicUsize>,
 21}
 22
 23impl TestDispatcher {
 24    pub fn new(seed: u64) -> Self {
 25        let scheduler = Arc::new(TestScheduler::new(TestSchedulerConfig {
 26            seed,
 27            randomize_order: true,
 28            allow_parking: false,
 29            capture_pending_traces: std::env::var("PENDING_TRACES")
 30                .map_or(false, |var| var == "1" || var == "true"),
 31            timeout_ticks: 0..=1000,
 32        }));
 33
 34        let session_id = scheduler.allocate_session_id();
 35
 36        TestDispatcher {
 37            session_id,
 38            scheduler,
 39            num_cpus_override: Arc::new(AtomicUsize::new(0)),
 40        }
 41    }
 42
 43    pub fn scheduler(&self) -> &Arc<TestScheduler> {
 44        &self.scheduler
 45    }
 46
 47    pub fn session_id(&self) -> SessionId {
 48        self.session_id
 49    }
 50
 51    pub fn drain_tasks(&self) {
 52        self.scheduler.drain_tasks();
 53    }
 54
 55    pub fn advance_clock(&self, by: Duration) {
 56        self.scheduler.advance_clock(by);
 57    }
 58
 59    pub fn advance_clock_to_next_timer(&self) -> bool {
 60        self.scheduler.advance_clock_to_next_timer()
 61    }
 62
 63    pub fn simulate_random_delay(&self) -> Yield {
 64        self.scheduler.yield_random()
 65    }
 66
 67    pub fn tick(&self, background_only: bool) -> bool {
 68        if background_only {
 69            self.scheduler.tick_background_only()
 70        } else {
 71            self.scheduler.tick()
 72        }
 73    }
 74
 75    pub fn run_until_parked(&self) {
 76        while self.tick(false) {}
 77    }
 78
 79    /// Override the value returned by `BackgroundExecutor::num_cpus()` in tests.
 80    /// A value of 0 means no override (the default of 4 is used).
 81    pub fn set_num_cpus(&self, count: usize) {
 82        self.num_cpus_override.store(count, Ordering::SeqCst);
 83    }
 84
 85    /// Returns the overridden CPU count, or `None` if no override is set.
 86    pub fn num_cpus_override(&self) -> Option<usize> {
 87        match self.num_cpus_override.load(Ordering::SeqCst) {
 88            0 => None,
 89            n => Some(n),
 90        }
 91    }
 92}
 93
 94impl Clone for TestDispatcher {
 95    fn clone(&self) -> Self {
 96        let session_id = self.scheduler.allocate_session_id();
 97        Self {
 98            session_id,
 99            scheduler: self.scheduler.clone(),
100            num_cpus_override: self.num_cpus_override.clone(),
101        }
102    }
103}
104
105impl PlatformDispatcher for TestDispatcher {
106    fn get_all_timings(&self) -> Vec<crate::ThreadTaskTimings> {
107        Vec::new()
108    }
109
110    fn get_current_thread_timings(&self) -> crate::ThreadTaskTimings {
111        crate::ThreadTaskTimings {
112            thread_name: None,
113            thread_id: std::thread::current().id(),
114            timings: Vec::new(),
115            total_pushed: 0,
116        }
117    }
118
119    fn is_main_thread(&self) -> bool {
120        self.scheduler.is_main_thread()
121    }
122
123    fn now(&self) -> Instant {
124        self.scheduler.clock().now()
125    }
126
127    fn dispatch(&self, runnable: RunnableVariant, priority: Priority) {
128        self.scheduler
129            .schedule_background_with_priority(runnable, priority);
130    }
131
132    fn dispatch_on_main_thread(&self, runnable: RunnableVariant, _priority: Priority) {
133        self.scheduler
134            .schedule_foreground(self.session_id, runnable);
135    }
136
137    fn dispatch_after(&self, _duration: Duration, _runnable: RunnableVariant) {
138        panic!(
139            "dispatch_after should not be called in tests. \
140            Use BackgroundExecutor::timer() which uses the scheduler's native timer."
141        );
142    }
143
144    fn as_test(&self) -> Option<&TestDispatcher> {
145        Some(self)
146    }
147
148    fn spawn_realtime(&self, f: Box<dyn FnOnce() + Send>) {
149        std::thread::spawn(move || {
150            f();
151        });
152    }
153}